Alexander Lancaster Co PA

I have hit a brick wall with my Alexander family. John Alexander 17 Nov 1807 - 22 Jan 1879 and his wife Sarah McCoy 1811-1885 lived in Bart Township, Lancaster Co. PA. Last record I found they sold property on 20th Mar 1868 in Bart. I know their 9 children's names but have been unable to find when and where they married or who they decended from. Both born PA. Any help would be appreciated.